[R-390] RE: Intial Power up ofa R30A Radio

[Drew Papanek]

Roger Agnew wrote:

  " I have heard that I should check the 2 capacitor cans and verify they =
   are good & functional due to the possibility they could be dried out or =
   shorted which can lead to damaging the Collins mechanical filters for =
   the band the radio is set to when powered up. "

Roger,

The capacitor whose failure can damage the mechanical filters is C-553.  It 
is located under the IF module and has one end connected to the bandwidth 
switch.   A friend of mine toasted a couple of his filters when that cap 
failed.

The mechanical filters are expensive and hard to find; replacing C-553 is 
cheap insurance.

The 2 can caps may need to be reformed by current-limited application of 
voltage.  They are especially prone to failure if branded General 
Instrument.  I had one fail and take out a resistor in the audio module, 
badly scorching the under chassis circuit board.

Check out Wei-i Li's comprehensive compilation of postings from this forum.  
Go to r-390a.net, references, Pearls of wisdom.  Simply Enthralling!

Drew

"Vicariously repairing and modifying R-390x via advice to others"

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